Flow control apparatus



Dec- 15, J E FLOW CONTROL APPARATUS Filed Sept. 5, 1946 [/vvE/vTo/e. JOHN E. COME/Ml BY H/s ATTORNEYS.

HARE/6:, K/ECH, F05 TEE & HARRIS BY v Patented Dec. 15, 1953 2,662,547 I C E FLOW CONTROL APPARATUS John E. Comeau, Culver City, Calif., assignor to The Garrett Corporation, Los Angeles, Calif., a corporation of California Application September 3, 1946, Serial No. 694,498

11 Claims.

My invention relates generally to fluid flow control apparatus and particularly to a constant weight fluid flow control device for controlling automatically the flow of air to the cabin of an aircraft or to other compartments.

One object of my invention is to provide a con stant weight fluid control device which is capable of supplying automatically the required mass of air per unit of time at a desired pressure to change the air with the required frequency to provide comfort to the passengers in the cabin of the aircraft regardless of the density and temperature of the. air.

Another object is to provide a constant weight fluid flow control device having means responsive to variations in pressure differential between spaced points in the air supply duct and to variations in density of the air supply, and to either, for maintaining automatically the required mass of air per unit of time.

Another object is to provide a fluid flow control device for use with an air supply duct having a restricted orifice or other means for producing a fluid pressure differential in the duct, said device being operative to control the setting of a valve movable in said duct.

Another object is to provide a device of the type indicated in which the flow control valve preferably is adjusted by-a reversible motor, the energization of which is controlled by the pressure responsive and density responsive means.

Another object is to provide a device of the character referred to employing a diaphragm which is responsive to variations in the pressure difierential between spaced points in the supply duct to actuate switch means for controlling the operation of the valve motor and also including a compensating means, preferably in the form of a bellows, which is responsive to variations in the density of the air in the duct to control the actuation of the switch means.

Another object is to provide a constant weight fluid fiow control device which is entirely automatic in operation and which is comparatively simple in construction and generally emcient in performing its intended function.

Further objects of my invention are set forth in the following specification and in the drawing, which is intended for illustration only.

In the accompanying drawing the constant weight fluid flow control device is illustrated in a part-sectional perspective view which also embodies a diagram of the electrical circuit for the valve operating motor.

Referring to the drawing in detail, the constant weight fluid flow control device is shown as applied to use in controlling the rate of fluid flow through a duct which may constitute the supply duct for supplying required mass of air per unit of time to the cabin of an airplane, the discharge end of a suitable air compressor (not shown) being connected to the end s cf the duct. Provided in the upstream end of the duct 5 is a pressure differential device, herein shown as a septum or partition 8 having a restricted orifice 9, the septum 8 thus dividing the duct 5 into a high pressure area Hi and a relatively lower pressure area H. It will be readily apparent that other means, such as a Venturi tube, may be employed for creating a pressure differential between spaced points within the supply duct 5, this invention not being limited to any specific means for producing a pressure differential.

Disposed in the downstream end of the duct 5 is a valve means indicated generally at it. While any suitable valve means may be utilized, I prefer to employ a valve of the butterfly type having a closure flap :5 carried by a shaft iii, the ends of which are rotatable in opposite sides of the duct. One end of the valve shaft I6 projects beyond the side of the duct and fast on this end is a worm wheel sector IT. The sector H is adapted to be rotated by a worm is fast on the armature shaft 19 of a reversible electric motor 20 mounted in any suitable manner adjacent the duct 5. It will be apparent that when the electric motor 29 is energized it will operate, through its armature shaft I 9, the worm is and the sector :1 to pivot the butterfly valve flap iii in either direction, depending upon the direction of rotation of the motor as controlled by means to be described hereinafter.

Formed integral with or as a separate member attached to the duct 5 is a hollow casing 23 having a septum or partition wall 24 dividing the easing into an upper chamber 25 and a lower chamber 25. The wall 2 has a relatively large opening 2'! across which extends a diaphragm 38, the peripheral edge of the diaphragm being suitably attached to the wall 24 to provide an airtight connection. The lower portion of the casing 23 is provided with an opening 3! communicating with the lower pressure area I within the duct 5. Held in the opening 35 is a cupshaped holder member 33 which may extend down into the duct 5. The holder member 33 supports a vaporor gas-filled density-responsive bellows element 35 having a hollow dome-shaped rigid cap 35a extending into the duct 5 beyond the holder member. A tube or conduit 35 communicates between the high pressure area it of the duct 5 and the lower chamber 26 of the easing 23 and a similar conduit 3? communicates between the lower pressure area H of the duct and the upper chamber 25 of the casing. It will be seen from the above that the fluid pressure differential occurring between the areas iii and H of the duct 5 will act to flex the diaphragm 3B and that the pressure of the air within the chamber 26 will cause expansion and contraction of the bellows element 35 in the manner well known to those versed in the art. Temperature changes in the air flowing in the duct 5 will be impressed on the bellows cap 35a, thereby causing the gas or vapor in the bellows to expand or contract and .9 thus cause the bellows to distend or shorten. The combined action of the bellows 35 under variations in density and the diaphragm 3% under variations in pressure serves to energize and deeergize the electric motor 28 through instrumentalities to be next described.

Pivoted on insulated studs 31 and 38 within the casing 23 are opposite switch members 39 and as having spring arms 59a and Mia. At their outer ends the members 35 and it have contact buttons and i2, respectively. The ends of the members 538a and Ma carry fiber cam-followers t3 and id-engageable with opposite sides of an edge-cam d carried by a shaft t6 journaled in the side of the casing 23. The folowers i3 and 34 are maintained in engagement with the cam 45 by means of a spring ll connected between the members 39 and Ml. During the supplying of pressurized air to the aircraft cabin the cam 45 and shaft 56 are rotated continuously by an electric motor 39 mounted on or adjacent the casing 23, the armature shaft of the motor it carrying a worm 5% which drives a worm wheel 52 fast on the shaft The switch members 39 and 4!: thus are continuously oscillated in generally parallel relationship to cause the contacts 4! and 2 to move in unison from side to side.

Pivoted on a stud 55 within the chamber 25 is a contact arm 56 having a contact 5? at its end adapted to engage the contacts ll and d2 of the switch members 39 and ill. Operatively connected to the contact arm 56 is a bell-crank lever 59 having a substantially horizontal arm 60 and a substantially vertical arm ill to which one end of a spring 62 is connected, the other end of the spring being anchored to a tension-adjusting stud 63 on the casing 23. The arm 6B of the bell-crank lever 59 is pivotally connected to one end of a third-class lever 64 which is pivoted on a pin t5. Substantially midway between its ends the lever 64 is pivotally connected to the upper clevis end of a push-rod 66 which extends downwardly through a hole in the diaphragm 3%. Nuts 6? screwed onto a threaded portion of the rod 56 and set up against opposite sides of the diaphragm 3i connect these parts together so that flexing of the diaphragm imparts vertical movement to the rod. Vertical movement of the rod 66 under the influence of the diaphragm 30 may be augmented or opposed by means of a first-class lever is which is pivoted at H and which has one end pivotally connected to he lower end of the rod 86 at E2. The other end of the lever is pivotally attached to an axial connector M secured to the upper end of the bellows element 35.

The reversible valve operating motor it has a pair of field windings, as is common in motors of this type, the branch circuit line 18 from one winding being connected to one switch member 39 and the branch circuit line ll of the other winding being joined to the other switch member 40. A ground'wire i8 is common to both windings. interposed in the lines 76 and 'H are normallyclosed limit switches at and ill, respectively, the actuating arms 82 of these switches being adapted to be engaged by the ends of the worm wheel sector ll as the latter is rotated in opposite directions and to open the circuit to the particular winding of the motor which is energized at the time. Electrical current is supplied through a main line st to the contact arm 56 and flows to either of the branch lines It and 11, depending upon which switch member 39 or 40 is engaged with the contact arm. The electrical. circuit may also include a manually operable switch 85 for initiating and arresting operation of the entire fluid flow control device. My improved constant weight fluid flow control device having been described in detail, the method of operation thereof is explained as follows:

To start the operation of the control device the main switch 85 is closed and the switch-actuating motor 2-9 thus is energized to rotate the cam 45 to cause the switch members 39 and 40 to be oscillated in unison by the single lobe 86 of the cam. Assuming that the contact arm 55 is in the position shown in the drawing, that is, with its contact 52' midway between the contacts ll and c2 of the respective members 39 and it, as the members are oscillated they will fail to engage the contact arm and thus electrical flow through the branch circuits l6 and H will be prevented and the butterfly valve 55 will remain stationary. The air compressor (not shown) is then started to effect the flow of pressurized air through the duct to the cabin of the airplane. Due to the restricted orifice 9, an area it of relatively high pressure is provided at the upstream side of the septum 3 and an area H of relatively lower pressure is produced at the downstream side of the septum, thus creating a pressure differential therebetween. In the present cabin pressurizin system the air compressor unit supplies air continuously and the improved control device merely regulates the flow of said pressurized air to the aircraft cabin without varying the output of the compressor unit.

It can be shown that the mass flow of air through an orifice varies in accordance with the following closely approximate law:

M C AV pAP where From this law, it will be apparent that in the present control, since the orifice area is constant, the device must sense changes in density p and changes in pressure differential AP, in order to maintain a desired mass flow. Since the density p is directly proportional to the absolute pressure and inversely proportional to the absolute temperature, the bellows 35 senses both of these variables in order to sense density. The diaphragm 30 senses variations in pressure differential AP.

While the apparatus herein described does not relate the variables pAP in the precise relationship set forth in the law above, it does relate such variables in a manner sufficiently close to such relationship as to provide a sensing of variations in mass flow sufliciently accurate for most practical purposes.

The air under pressure is transmitted from the relatively high and lower pressure areas ii! and H of the duct 5 through the conduits 36 and 3-? intc the respective compartments 2E5 25 and the pressure differential thus created on opposite sides of the diaphragm causes the latter to flex. If the pressure differential is greater than a predetermined value the diaphragm Zat will act through the push-rod 6G, lever 65 and bell-crank lever 50 to pivot the contact arm 53 in an upward direction to cause its contact 5'? to move toward the contact H of the switch member 39. Conseouently, when the switch member 39 pivots Zownwardly under the action of the cam 35 its contact ll will momentarily engage the contact to close the electrical circuit to the valveoperating motor through the branch, line it and limit switc. iii. The motor 26 thus is en ergiced and functions through its worm is to rotate the worm-wheel sector ii in a direction to pivot the butterfly valve flap it toward closed position to reduce the rate of flow of pressurized air to the cabin. Due to the fact that the switch member 3%? is constantly oscillated by the earn iii 21131285 contact with arm at for a length of time proportional to the instantaneous departure of the actual mass now from the desired value any moment, the circuit to the motor is peri dically opened and closed and the motor interinitt-ently energized or pulsed to cause the valve 5 to move with, a rapidity proportional to the need for changing its position. It will be noted by reference to the drawing that the lobe of the cam has a gradual incline and an abrupt return edge so that the switch member will rnove gradually toward the contact arm be disengaged from the arm at a relatively st rate. it will be apparent that the oscillations of the switch members and til may be of any desired frequency, provided the frequency is greater than twice the natural hunting frequency of the system controlled, this relationship being necessary to prevent hunting.

as valve is is moved toward a closed position in the manner explained above, the pressure decrease so that the diaphragm will act to gradually lower the contact arm to increase the gap between the contacts d Eventually, the contact 5? will be discentrally of; the contacts ll and 42 and thus the valve motor to will be (is-energized and the valve is will remain in the position to which it has been adjusted until again acted upon the motor drive. Assuming now that the'press e differential becomes less a predeterneo. required vaue, flexing of the diaphragm will decrease and thus the contact arm will e moved dowi wardly to cause its contact 57 to oach the contact d2 of the switch member to. he switch member lil is oscillated the branch circu t 2? will be periodically closed to cause intent energiration of the motor Zll in a dito rotate the valve l5 toward open It essential that the contact buttons 1 lightly with the contact of to revent undue force thereagainst w would be v.anslrlitted through the arm le l roe. to impair effectiveness of the diaphre gin 3c and bellows In the present e suing arm: and ind are employed for the purpose of a yielding engagement of the contacts.

as thus far explained, the position of the con t arm is controlled by the pressure difresponsive diaphragm Ell. However, the air, which is supplied to the chamber 72% also acts a ainst the vaporor gas-filled bellows element on to cause contraction or expansion in the v.ctb. oereof in the manner well-known to those ve 1n the variation in the length othe bellows element is transmitted through the lever to the push-rod 65 to alter the positio of the contact arm It is thus seen that cicn or" the contact arm to is determined troll" by the combined efiects of moveof the so in response to variin fluid pressure differential, and moveall ment of the bellows 35 in response to variations in fluid density. Since gaseous fluid density varies'with changes in temperature and pressure, the bellows element 35 is responsive to variations in these properties of the air. The duration of the time of contact between contact 5'1? and either contact ll or 32 for any one revolution of the cam in is directly proportional to the disp1acement of arm 55 from its neutral position, and this displacement, in turn, is directly proportional to the variation of the mass flow of air from the desired normal flow. Because the position of the contact arr 56 determines the adjustment or setting of the butterfly valve and the arm is adjusted automatically in accordance with variations in fluid pressure differential and in the f u-id density, there is conveyed through the duct 5 a mass of air per unit of time which is constant regardless of variations in the pressure and temperature of the air. will be apparent that by adjusting the tension or" the spring 82 the force necessary to pivot the contact arm 55% may be varied and since this force responsivc to variations in fluid pressure differential and fluid density, the desired mass of air per unit of time may be readily obtained. My control device thus supplies automatically the required mass of air per unit of time to the cabin of the aircraft and acts to change the air therein with the required frequency to provide C0111- i'ort to the passengers regardless of the density and temperature of the air.

While I have herein shown and described the constant weight flow control device as embodied in a preferred construction having its elements arranged in a specific manner, it will be apparout that various changes and modifications may readetherein without departing from the spi; of my invention and I therefore reserve the right to all such changes as fall within the scope of the appended claims.

I claim as my invention:

1. A constant weight fluid flow control device, including: a duct for conveying fluid; a septum in said duct and provided with a restricted opening, said septum and opening providing in said duct a high pressure region and a relatively lower pressure region for efiecting a fluid pressure differential therebetween; a casing; a diaphragm disposed in said casing and dividing said casing into two compartments; a first conduit connected. between said high pressure region and one of said compartments; asecond conduit connected between said lower pressure region and the other of said compartments; rotatable valve means in said duct disposed downstream from said opening for regulating the rate of fluid flow through said duct, said valve means having a worm wheel sector; a reversible electric motor having a worm meshing with said sector for rotating said valve means in either direction; a main electric circuit having a pair of branch circuits for said motor; switch means in said branch circuits and operatively connected to said. diaphragm, said diaphragm being responsive to variations in fluid pressure differential in said compartments to open and close said switch means; and means responsive to variations in fluid density in the high pressure region of said duct to open and close said switch means.

2. A constant weight iiuid flow control device, including: a duct for conveying d; a septum in said duct and provided with a rest ct :1 opening, said septum opening providing in aid pressure region for effecting a fluid pressure differential therebetween; a hollow casing having a partition wall provided. with an opening; a diaphragm extending across said opening, said wall and said. diaphragm dividing the interior of said casing into two compartments; a, first conduit connected between said high pressure region and one of said compartments; a second conduit connected between said lower pressure region and the other of said compartments; rotatable valve means in said duct disposed downstream from said septum for regulating the rate of fluid flow through said duct; a reversible electric motor for rotating said valve means in either direction; amain electric circuit having a pair of branch circuits for said motor; switch means in each oi. said branch circuits; a movable contact element connected in said main circuit and. engageable with either of said switch means to close either of said branch circuits to said motor; actuating means operatively connected. between said con tact element and said diaphragm for moving said contact element, said diaphragm being responsive to variations in fluid p essure differential in said compartments to operate said actuating means; and means responsive to variations in static pressure in said duct upstream of said septum and temperature downstream of said septum to operate said actuating means.

3. A constant weight fluid flow control device, including: a duct for conveying fluid; a septum in said duct and provided with a restricted opening, said septum and opening providing in said duct a high pressure area and a relatively lower pressure area for eflecting a fluid pressure differential therebetween; a hollow casing having a partition wall provided with an opening; a diaphragm extending across said opening, said partition and said diaphragm dividing th interior of said easing into two compartments; a first conduit connected between said high pressure area and one of said compartments; second conduit connected between said lower pressure area and the other of said compartments; rotatable valve means in. said duct disposed downstream from said septum for regulating the rate of fluid through said duct; a reversible electric motor for rotating valve means in either direction; a main electric circuit having a pair of branch circuits for said motor; a movable switch member in each of branch circuits, said switch members being disposed in spaced relationship; a contact element connected in said main circuit and adjustable between said switch members, contact element being operatively connected to diaphragm to adapt it to be adjusted thereby, said diaphragm being adapted to be flexed in response to variations in fluid pressure differential in said compartments; means for intermittently moving said switch members into and out of engagement with said contact element, to open or close either of said branch circuits, position of said contact element as adjusted by the flexing of said dian determining the duration of engagement ier switch member with said contact element to control the duration of intermittent ene ation of either of said branch circuits; and ilieans responsive to variations in fluid density in said duct to adjust said contact element.

4. A constant weight fluid flow control device as defined in claim 3 in which said means for internittently moving said. switch means includes continuously operating cam means engaging both switch means.

5. A constant weight fluid flow control device as defined in claim 3 and including limit switches in circuit with said switch means for opening said branch circuits upon rotative movement or" said valve means in either direction to predetermined positions.

6. A constant weight fluid flow control device as defined in claim 2 and including means for regulating the resistance to movement of said contact arm under the influence of said diaphragm to vary the weight fluid flow to be maintained at a constant value by said device.

'7. A constant weight fluid flow control device, including: a duct for conveying fluid; a septum in said duct and provided with a restricted opening, said septum and opening providing in said duct a high pressure area and a relatively lower pressure area for effecting a fluid pressure differential therebetween; a hollow casing having a partition wall provided with an opening; a diaphragm extending across said opening, said partition and said diaphragm dividing the interior of said easing into two compartments; a first con.- duit connected between said high pressure area and one of said compartments; second conduit connected between said lower pressure area and the other of said compartments; rotatable valve means in said duct disposed downstream from said septum for regulating the rate of fluid flow through said duct; a reversible electric motor for rotating said valve means in either direction; a main electric circuit having apair of branch circuits for said motor; a movable switch member in each of said branch circuits, said switch members being disposed in spaced relationship; a contact element connected in said main circuit and adjustable between said switch members, said contact element being operatively connected to said diaphragm to adapt it to be adjusted thereby, said diaphragm being adapted to be flexed in response to variations in fluid pressure differential in said compartments; means for intermittently moving said switch members into and out of engagement with said contact elements, to open or close either of said branch circuits, the position of said contact element as ad.- justed by the flexing of said diaphragm determining the duration of engagement of either switch member with said contact element to control the duration of intermittent energization of either of said branch circuits, said means for intermittently moving said switch means including cam means and power means for continuously operating said cam means, said cam means engaging both switch means and being operative to simultaneously move both said switch means; and means responsive to variations in fluid density in said duct to adjust said contact element.

8. A constant weight fluid flow controlling device, including: a duct for conveying fluid; means in said duct for producing a pressure differential therein; movable valve means in said duct for regulating the rate of fluid flow therethrough, reversible operating means for moving said valve means toward open and closed positions, said reversible operating means having energizable means for effecting valve opening movement of said reversible operating means and energizable means for effecting valve closing movement of said reversible operating means; movable means for energizing only one of said energizable means at a time for efiecting operation of the reversible operating means to cause it to operate in either direction; and means responsive to variations in fluid pressure differential produced by said differential producing means, means responsive to variations in fluid pressure in the higher pressure region of said duct and to the temperature in the lower pressure region of said duct for effecting movement of said energizing means.

9. A constant weight fluid flow control device, including: a duct for conveying fluid; a septum in said duct and provided with a restricted opening, said septum and opening providing in said duct a high pressure area and a relatively lower pressure area for eflecting a, fluid pressure differential therebetween; a a partition wall provided with an opening; a diaphragm extending across said opening, said partition and said diaphragm dividing the interior of said casing into two compartments; a first conduit connected between said high pressure area and one of said compartments; second conduit connected between said lower pressure area and the other of said compartments; rotatable valve means in said duct disposed downstream from said septum for regulating the rate of fluid flow through said duct; a reversible electric motor for rotating said valve means in either direction; a main electric circuit having a pair of branch circuits for said motor; a movable switch member in each of said branch circuits, said switch members being disposed in a spaced relationship; a contact element connected in said main circuit and adjustable between said switch members, said contact element being operatively connected to said diaphragm to adapt it to be adjusted thereby, said diaphragm being adapted to be flexed in response to variations in fluid pressure differential in said compartments; means for intermittently moving said switch members into and out of engagement with said contact element, to open or close either of said branch circuits, the position of said contact element as adjusted by the flexing of said diaphragm determining the duration of engagement of either switch member with said contact element to control the duration of intermittent energization of either of said branch circuits; and means responsive to variations in fluid pressure and temperature in said duct to adjust said contact element.

10. A constant weight fluid flow control device, including: a duct for conveying fluid; a septum in said duct and provided with a restricted opening, said septum and opening providing in said duct a high pressure area and a relatively lower pressure area for effecting a fluid pressure differential therebetween; a hollow casing having a partition wall provided with an opening; a diaphragm extending across said opening, said partition and said diaphragm dividing the interior of said casing into two compartments; a first conduit connected between said high pressure area and one of said compartments; second conduit connected be tween said lower pressure area and the other of said compartments; rotatable valve means in said duct disposed downstream from said septum for regulating the rate of fluid flow through said duct; a reversible electric motor for rotating said valve means in either direction; a main electric circuit having a pair of branch circuits for said motor; a movable switch member in each of said branch circuits, said switch members being disposed in spaced relationship; a contact element connected in said main circuit and adjustable between said switch members, said contact element being operatively connected to said diaphragm to adapt it to be adjusted thereby, said diaphragm being adapted to be hollow casing having flexed in response to variations in fluid pressure diflerential in said compartments; means for intermittently moving said switch members into and out of engagement with said contact elements, to open or close either of said branch circuits, the position of said contact element as adjusted by the flexing of said diaphragm determining the duration of engagement of either switch member with said contact element to control the duration of intermittent energization of either of said branch circuits, said means for intermittently moving said switch means including cam means and power means for continuously operating said cam means, said cam means engaging both switch means and being operative to simultaneously move both said switch means; and means responsive to variations in fluid pressure and temperature in said duct to adjust said contact element.

11. A constant weight fluid flow control device, including: a duct for conveying fluid; a septum in said duct and provided with a restricted opening, said septum and opening providing in said duct a high pressure area and a relatively lower pressure area for eifecting a fluid pressure differential therebetween; a hollow casing having a partition wall provided with an opening; a diaphragm extending across said opening, said partition and said diaphragm dividing the in terior of said casing into two compartments; a first conduit connected between said high pressure area and one of said compartments; second conduit connected between said lower pressure area and other or said compartments; rotatable valve means in said duct for regulating the rate of fluid flow through said duct; a reversible electric motor for rotating said valve means in either direction; a main electric circuit having a pair of branch circuits for able switch member in each cuits, said switch members being disposed in spaced relationship; a contact element connected in said main circuit and adjustable between said switch members, said contact element being operatively connected to said diaphragm to adapt it to be adjusted thereby, said diaphragm being adapted to be flexed in response to variations in fluid pressure differential in said compartments; means for intermittently moving said switch members into and out of engagement with said contact element, to open or close either of said branch circuits, the position of said contact element as adjusted by the flexing of said diaphragm determining the duration of engagement of either switch member with said contact element to control the duration of intermittent energization of either of said branch circuits; and means responsive to variations in fluid density in said duct to adjust said contact element.

said motor; a movof said branch cir- JOHN E. COMEAU.

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